Photosensitive elements for image-reproduction are well-known in the graphics arts industry. Such elements are exposed to actinic radiation through an image-bearing transparency, such as a color separation transparency, to produce a duplicate image that is either a positive or negative of the transparency. Positive-working elements produce a duplicate image of the transparency; that is, the colored regions of the transparency are colored and the uncolored regions in the transparency are uncolored in the final image. Negative-working elements produce an image that is the reverse of the transparency; that is, the colored regions of the transparency are uncolored and the uncolored regions in the transparency are colored in the final image. After imagewise exposure, the photosensitive elements are developed by washout of soluble image areas, toning with a colorant, peeling apart, or combinations of these techniques.
In general, such photosensitive elements offer a limited choice of receptors for the final image. For example, in proofing applications it generally is not possible to form the final image (the "proof") on paper that will be used for the printing run. Thus, the proof may not look exactly the same as the printed copy and considerable experience is required to evaluate the proof.
In addition to limited choices of receptor for the final image, many photosensitive elements for image reproduction have the added disadvantage of requiring washout by an organic solvent. For example, U.S. Pat. No. 4,053,313 (Fan) discloses a photosensitive element comprising a solvent-processable photosensitive layer, a tonable elastomeric layer, and a support, that is processed (i.e., washed-out) by a mixture of water and organic solvent. The elements disclosed in U.S. Pat. Nos. 4,376,158 and 4,376,159 (Speckler) require aqueous base for washout. Use of organic solvents or aqueous bases frequently is undesirable due to flammability, toxicity, corrosion and/or waste disposal considerations.
Thus there continues to be a need for improved photosensitive elements capable of reproducing images on a variety of receptors and that can be processed with aqueous solutions, preferably with ordinary tap water.